Compressed air supply device for a utility vehicle

ABSTRACT

A compressed air supply device is provided for a utility vehicle, having a compressor which can be driven by a drive via a pneumatically switchable clutch, and a valve which can be activated by an electrical signal in order to optionally feed compressed air to a switching inlet of the clutch. The compressed air, which is fed to the switching inlet via the valve, is extracted from a compressed air preprocessing system via a non-return valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No.PCT/EP2007/004420, filed May 16, 2007, which claims priority under 35U.S.C. §119 to German Patent Application No. DE 10 2006 023 728.5, filedMay 19, 2006, the entire disclosures of which are herein expresslyincorporated by reference.

This application contains subject matter related to U.S. applicationSer. Nos. 12/273,242, 12/273,382, and 12/273,388, entitled “Method forControlling or Regulating the Air Pressure in a Compressed Air SupplyDevice,” “Compressed Air Supply System for a Utility Vehicle,” and“Compressed Air Supply System for a Utility Vehicle,” respectively, allfiled on an even date herewith.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a compressed air supply system for autility or commercial vehicle, with a compressor drivable by a drive viaa pneumatically switchable coupling, and a valve, actuatable by means ofan electrical signal, for the selective delivery of compressed air to aswitch input of the coupling.

Compressed air supply systems are of central importance for utilityvehicles. In particular, the brake system or a pneumatically brakedutility vehicle requires compressed air, as do numerous furtherconsumers, for example air suspensions or lift axle devices. Thecompressed air to be prepared and distributed by the compressed airsupply system is delivered by a compressor which is generally driven bythe internal combustion engine of the utility vehicle. In a conceptwhich is common in this regard, the compressor is coupled to theinternal combustion engine via a pneumatically switchable coupling, thecompressed air for the pneumatic activation of the coupling beingextracted, in turn, from the compressed air supply system. An example ofa system of this type is given in DE 39 23 882 C2.

Owing to the switchability of the coupling, the operation of thecompressor can be interrupted, as required, for example during theregeneration phases of the filter unit. The decoupling of the compressorfrom the internal combustion engine can likewise be used in a directedmanner with regard to the energy balance of the utility vehicle.

However, implementing a concept with a switchable coupling is notwithout problems in all aspects. In particular, however theimplementation of a concept with a switchable coupling, is not withoutits problems in all aspects. In particular, it is desirable to makeavailable short switching times for the coupling, so that, especiallywhen a vehicle is operating with a frequent change of the coupling, noundesirable effects arise on account of switching delays.

The object on which the invention is based is to make a available acompressed air supply system with a switchable coupling on the basis ofa cost-effective and particularly functionable concept, while at thesame time, in particular, short switching times are to be ensured.

The invention builds on the generic compressed air supply system in thatthe compressed air delivered to the switch input via the valve isextracted from a compressed air preprocessing system via a nonreturnvalve. In order to ensure a high switching speed in the case of apneumatic valve, delivery to a pneumatic valve must preferably bemaintained at a certain pressure level. Consequently, during the openingof the valve, a sufficient pressure is immediately present which canthen also quickly cause the changeover of the coupling via the shortline to the coupling. Since the compressed air for changing over thecoupling is preferably extracted from a compressed air preprocessingsystem which also supplies other consumers with compressed air, apressure level, sufficient during the ventilating operation, in the lineleading to the pneumatic valve, is often ensured by an additionalpressure reservoir. This is unnecessary if the compressed air deliveredto the switch input via the valve is extracted via a nonreturn valve,since the latter prevents a pressure breakdown in the pressure deliveryline on account of other effects in the region of the compressed airpreprocessing system and the consumers connected to it.

According to a preferred embodiment, there may be provision for thenonreturn valve to be integrated into the compressed air preprocessingsystem. An essential constituent of the compressed air preprocessingsystem is a valve housing which has at least one circuit protectiondevice and which makes it possible readily to incorporate a furthernonreturn valve by dealing with a merely structural task. However, theexternal arrangement of the nonreturn valve may also likewise beenvisaged. There is usefully provision for the line which leads from thenonreturn valve to the valve activating the coupling to be connected toa valve-housing connection specifically provided for this purpose.

There is usefully provision for the valve to be arranged in the regionof a fresh air supply to the compressor. Generally, high temperaturesprevail in the region of the internal combustion engine, and thereforethe switching members, that is to say, in particular, pneumaticallyand/or electrically activatable valves, must be designedcorrespondingly, thus entailing correspondingly high costs. In theregion of the air supply to the compressor, that is to say, inparticular, at the intake connection piece of the latter, comparativelylow temperatures prevail, so that a valve can be used, without specialaccount being taken of temperature resistance. In addition, thearrangement mentioned affords the advantage that a particularly shortline path may be provided between the valve and the switchable coupling,thus shortening the changeover times of the coupling. This isadvantageous particularly in plants which are intended to bring about afrequent changeover of the coupling.

There is usefully provision for the valve to be an electricallypilot-controllable pneumatic valve. Such a valve, because of the highair throughput achievable, makes it possible to have a rapid pressurebuild-up at the switching member of the coupling, so that this measure,too, increases the switching speed.

The compressed air supply system according to the invention may bedesigned, for example, such that the electrical signal is made availableby a pressure switch which responds to a pressure in a compressed airpreprocessing system. One reason for decoupling the internal combustionengine and compressor may be the presence of a sufficient pressurewithin the compressed air preprocessing system or in the region of theconsumer connections. It is consequently useful to convert this pressureinto an electrical signal which then, in turn, causes the decoupling ofthe internal combustion engine and compressor. With an appropriatecoordination of pressure switch and valve, the signal can be deliveredto the valve directly or by means of further electrical or electroniccomponents.

There may likewise usefully be provision for the electrical signal to bemade available by an electronic control which receivespressure-dependent input signals. The signal from the pressure switch isthus first delivered to an electronic control which then, ifappropriate, outputs the signal for the valve. The advantage of this isthat other parameters present in the utility vehicle can be taken intoaccount in terms of the operation of changing over the coupling.

For example, there may be provision for the electrical signal to be madeavailable by an electronic control which receives temperature-dependentinput signals. Thus, for example, the temperature in the region of thecompressor can be measured, in order, in the case of an increasedtemperature, to bring about a decoupling of the compressor from theinternal combustion engine.

It is likewise possible for the electrical signal to be made availableby an electronic control which receives input signals dependent on theinput-side and/or output-side rotational speed of the coupling. Amonitoring of the rotational speeds in the region of the coupling mayalso be useful, for example with a view to fault diagnosis.

According to a particularly advantageous embodiment of the invention,there is provision for the electronic control to be integrated into acompressed air preprocessing system. This can be implemented, inpractice, in that the conventional electronic control of the compressedair preprocessing system is extended to include the functionality ofcoupling activation.

It is also conceivable, however, that the electronic controlcommunicates via an interface with a control integrated into acompressed air preprocessing system. On this basis, the conventionalelectronic control of the compressed air preprocessing system can remainlargely unchanged, and the switching functionality for the coupling canbe available externally.

The invention relates, furthermore, to a utility vehicle having acompressed air supply system according to the invention.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of one ormore preferred embodiments when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic illustration of a compressed air supplysystem according to the invention;

FIG. 2 shows a diagrammatic illustration of a compressed air supplysystem according to the invention; and

FIG. 3 shows a diagrammatic illustration of a compressed air supplysystem according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following description of the drawings, the same reference symbolsdesignate identical or comparable components.

FIG. 1 shows a diagrammatic illustration of a compressed air supplysystem according to the invention. A compressed air preprocessing system26 is illustrated. By means of this, delivered compressed air isfiltered and distributed to various compressed air consumers. An inputconnection 44 is provided, which is connected to a compressor 14provided outside the compressed air preprocessing system 26. Anextraneous filing connection 46 is arranged parallel to the inputconnection 44. The compressed air delivered to one of the inputs 44, 46is delivered to a filter unit 48 and from there, via a nonreturn valve50, to a main supply line 52. Arranged in parallel on the main supplyline 52 are two overflow valves 54, 56, via which connections 58, 60 forservice brake circuits of the utility vehicle, are supplied withcompressed air. A throttle 62, 64 and a nonreturn valve 66, 68 arearranged in each case parallel to the overflow valves, according to thepresent embodiment a flow parallel to the flow through the overflowvalves 54, 56 being made possible from the main supply line 52 to theconnections 58, 60 of the service brake circuits. As a result,particularly during the refilling of the system, an early filling of theservice brake circuit reservoirs can take place even when the pressuresin the main supply line 52 are low. It is likewise possible to providethe nonreturn valves in the opposite direction, this refilling benefitbeing dispensed with. As a result, an afterfilling of secondaryconsumers from the reservoirs of the service brake circuits is then madepossible. Furthermore, a pressure limiter 70 is provided in the mainsupply line 52. Two further lines branch off in parallel on thepressure-limited side of the pressure limiter 70, a connection 76 forthe parking brake and the trailer brake system being supplied by oneline via an overflow valve 72 and a nonreturn valve 74. The other line,via a nonreturn valve 42 and an overflow valve 78, supplies a connection80 which is provided for actuating the compressor coupling 12. Theoverflow valve 78 is followed in a branching-off line by a furtheroverflow valve 82, via which a further secondary consumer connection 84is supplied.

A plurality of pressure sensors 86, 88, 90, 92 are connected to theelectronic control 32, the pressure sensor 88 measuring the pressure atthe service brake connection 58, the pressure sensor 90 measuring thepressure at the service brake connection 60 and the pressure sensor 62measuring the pressure directly downstream of the overflow valve 72 forthe connection 76 of the parking brake and trailer. Furthermore, atemperature sensor 94 and a heating 96 are connected to the electroniccontrol 32. Moreover, three solenoid valves 98, 100, 102 are connectedto the electronic control 32, the pressure controller solenoid valve 98,the regeneration solenoid valve 100 and a solenoid valve 102 for theadditional pressure control of the overflow valve 72. The solenoidvalves 78, 100, 102 are designed as 3/2-way valves and all are closed inthe currentless state. In the closed state, the pressure of the mainsupply line 52 is present at the inputs of the solenoid valves 98, 100,102. To initiate a regenerating operation, it is necessary to applycurrent to the regeneration solenoid valve 100 and the pressurecontroller solenoid valve 98 and thus transfer them into their statewhich is not illustrated. The result of this is that dry compressed airis extracted from the service brake reservoirs via the main supply line52 and then, bypassing the nonreturn valve 50, flows in the oppositedirection, via the regeneration solenoid valve 100, a further nonreturnvalve 104 and a throttle 106, through the filter unit 48, in order then,via a discharge valve 106 changed over into its switching position, notillustrated, on account of the changeover of the pressure controllersolenoid valve 98, to flow out to a discharge 108 and from there intothe atmosphere. The compressor 14 already mentioned, an internalcombustion engine 10 and a switchable coupling 12 connecting thecompressor 14 to the internal combustion engine 10 are illustratedoutside the compressed air preprocessing system 26. The compressor 14has an intake connection piece 22, via which the air to be compressed issucked in. In the region of this air delivery, a 3/2-way valve 18 isarranged, which in the present case, as separately illustrated onceagain, is designed as an electrically pilot-controlled pneumatic valve.The pneumatic valve 18 has an input connection 110, to which a line 112leading to the coupling connection 80 is connected. In this line 112, anonreturn valve 40 is arranged which allows a flow from the couplingconnection 80 to the valve 18 and prevents an opposite flow. The valve18 has an output connection which is coupled to a switch input 20 of thecoupling 12 via a line 116. Via an electrical input 118 for the purposeof delivering a signal 16, the valve is connected to the electroniccontrol 32 of the compressed air preprocessing system 26 and to groundwhich is picked off at a central plug 120.

The compressed air supply system according to FIG. 1 operates as followsin terms of the switchable coupling 12. When the coupling 12, closed inthe non-pressure-activated state, is to be opened, for example in thecase of a regeneration already mentioned, the electronic control 32transmits an output signal 16 to the electrically pilot-controlledpneumatic valve 18. The valve 18 opens, and a connection is thereby madebetween the coupling connection 80 of the compressed air preprocessingsystem 26 and the switch input 20 of the coupling 12. By means of theventilation of the switch input 20, the coupling 12 is opened and thecompressor 14 is stopped. To close the coupling 12, the application ofcurrent to the electrical input 118 is discontinued again, so that theswitch input 20 is vented. A short switching time is ensured by thenonreturn valves 40, 42. The nonreturn valve 42 prevents a backflow ofcompressed air out of the line 112 in the direction of the branches ofthe service brake connections 58, 60 and of the connection for theparking brake and the trailer. The nonreturn valve 40 additionallyprevents a backflow out of the line 112 to the secondary consumerconnection 84. Depending on the design of the plant and on therequirements in terms of the switching time, one of the nonreturn valves40, 42 may be sufficient. The nonreturn valves 40, 42 thus ensure that acertain pressure level can always be maintained in the intact line 112,so that, during the changeover of the valve 18, a rapid pressurebuild-up at the switch input 20 of the compressor 12 is ensured. Anadditional reservoir in the region of the line 112, by means of whichreservoir the maintaining of such a pressure level could likewise beensured, is therefore unnecessary. Between the connection 80 and thenonreturn valve 40, further consumers may also be connected, for exampleexhaust gas purification, an engine brake and/or transmissionactivation, for example exhaust gas purification, an engine brake and/ortransmission activation.

FIG. 2 shows a diagrammatic illustration of a compressed air supplysystem according to the invention. Numerous properties of the embodimentaccording to FIG. 2 are identical to the embodiment according to FIG. 1,for example also the preferred arrangement of the electricallypilot-controlled pneumatic valve 18 in the region of the air inlet ofthe compressor 14, even though this is not illustrated here. In contrastto the embodiment according to FIG. 1, in the embodiment according toFIG. 2 an external control 36 is provided in addition to the electroniccontrol 34 in the compressed air preprocessing system 28. The externalcontrol 36 is suitable for communicating with the internal control 34via an interface 122 which is preferably made available by the centralplug 120. An interface 124 with other vehicle components is likewiseprovided, for example with a vehicle management computer via a CAN bus.The interfaces 122, 124 may be combined in structural terms. FIG. 2shows, furthermore, that a rotational speed sensor 126 may be arrangedon the input side of the coupling 12 and a further rotational speedsensor 128 may be arranged on the output side of the coupling 12.Moreover, a temperature sensor 130 is provided at the compressor 14. Thesignals from the sensors 126, 128, 130 are delivered to the externalcontrol 36 and are taken into account by the latter with regard to theactivation of the valve or are utilized in another way, for example forfunction monitoring, and/or are transferred in original or processedform via the interfaces 122, 124.

The useful determination of the rotational speeds and of the temperaturemay also be provided in conjunction with the embodiment according toFIG. 1, even though this is not illustrated there. The correspondingdata are then delivered to the internal control 32 of the compressed airpreprocessing system 26.

FIG. 3 shows a diagrammatic illustration of a compressed air supplysystem according to the invention. The compressed air supply systemillustrated here is illustrated in the form of a plurality ofdistributed individual subassemblies. In particular, a pressurecontroller 130 with an attached filter unit 48, a multiple-circuitprotection valve 132, pressure limiters 134, 136 and an electroniccontrol 38 are illustrated. The components may in reality be distributedin the way described. However, the distributed illustration may also beunderstood in the sense of a functional division, in reality thepressure controller, multiple-circuit protection valve, pressurelimiters and/or electronic control being implemented in an integratedmanner, for example as illustrated in connection with FIGS. 1 and 2.

In the embodiment according to FIG. 3, once again, a compressor 14 iscoupled with an internal combustion engine 10 via a switchable coupling12. The compressor 14 delivers compressed air to the pressure controller130, from where the compressed air is transferred to themultiple-circuit protection valve 132. The multiple-circuit protectionvalve 132 distributes the compressed air to the reservoirs 138, 140 andother connections, one of which is illustrated as a connection providedwith a pressure limiter 136. A further connection is the couplingconnection 80, likewise supplied via a pressure limiter 134. Compressedair is delivered to the electrically pilot-controlled pneumatic valve 18from the coupling connection 80 via the nonreturn valve 40 which ensuresthe switching times. The valve 18 is activated by means of theelectronic control 38 which likewise communicates via the interface 124with the internal combustion engine or with an engine control. Theelectronic control 38 has a plurality of inputs 142, 144, 146. Theinputs 142, 144 symbolize the possibility of supplying the control 38with temperature, pressure and/or rotational speed information, forexample measured by the pressure sensors 88, 90 of the service brakecircuits, and/or by the rotational speed sensors 126, 128 on the inputside and the output side of the coupling 12. On the pressure controller130, a pressure switch 24 is provided. This is connected to the input146 of the electronic control 38. The electronic control 38 can thus besupplied with a pressure-dependent electrical signal.

The compressed air supply system according to FIG. 3 operates asfollows. On the basis of the information made available via the inputs142, 144, 146 and the interface 124, the electronic control 38 candeliver an electrical signal 16 to the valve 18, so that the latterchanges over and opens the coupling 12 by virtue of the ventilation ofthe switch input 20. The decision to output the signal 16 can then takeplace on the basis that pressures, temperatures or rotational speedsmeasured by sensors make it necessary to open the coupling 12. Inparallel with this, however, the opening of the coupling may also takeplace on the basis of the signal output by the pressure switch 24. Ifcomponents of the embodiment illustrated in FIG. 3 experience a defect,so that, for example, the pressure levels in the service brake circuitsare no longer measured reliably, an opening of the coupling 12nevertheless takes place because of the presence of the pressure switch24 and of the switch functionality thereby made possible, thuspreventing destruction of said coupling due to the defects outlined.

It is likewise possible, in addition to the variant illustrated in FIG.3, to deliver the output signal from the pressure switch 24 directly tothe valve 18, so that, even in the event of a complete failure of theelectronic control 38, an opening of the coupling 12 can take place.

The embodiments described in connection with FIGS. 1 to 3 make itpossible to have various advantageous types of functioning. For example,if the switching of the coupling fails, pressure control may be carriedout by the pressure controller of the compressed air preprocessingsystem, that is to say, in the case of an electronic compressed airpreprocessing system, by the discharge valve 106 and the assignedsolenoid valve 98. Furthermore, it is useful that the functioning of thevalve 18 activating the coupling be monitored for plausibility. In thisregard, the pressure values of a pressure sensor present in any case orof a pressure sensor specifically provided for this purpose may be used.In the event of a break of the line 116 between the valve 18 and thecoupling 12, the valve 18 is transferred into its closed state, andfurther pressure control takes place, once again, via the compressed airpreprocessing system, in particular the discharge valve 106 and thesolenoid valve 98.

TABLE OF REFERENCE SYMBOLS

-   -   10 Drive    -   12 Coupling    -   14 Compressor    -   16 Signal    -   18 Valve    -   20 Switch input    -   22 Fresh air supply    -   24 Pressure switch    -   26 Compressed air preprocessing system    -   28 Compressed air preprocessing system    -   30 Compressed air preprocessing system    -   32 Electronic control    -   34 Electronic control    -   36 Electronic control    -   38 Electronic control    -   40 Nonreturn valve    -   42 Nonreturn valve    -   44 Input connection    -   46 Extraneous filling connection    -   48 Filter unit    -   50 Nonreturn valve    -   52 Main supply line    -   54 Overflow valve    -   56 Overflow valve    -   58 Connection service brake circuit    -   60 Connection service brake circuit    -   62 Throttle    -   64 Throttle    -   66 Nonreturn valve    -   68 Nonreturn valve    -   70 Pressure limiter    -   72 Overflow valve    -   74 Nonreturn valve    -   76 Connection parking brake/trailer    -   78 Overflow valve    -   80 Connection coupling    -   82 Overflow valve    -   84 Connection secondary consumer    -   86 Pressure sensor    -   88 Pressure sensor    -   90 Pressure sensor    -   92 Pressure sensor    -   94 Temperature sensor    -   96 Heating    -   98 Solenoid valve    -   100 Solenoid valve    -   102 Solenoid valve    -   104 Nonreturn valve    -   106 Discharge valve    -   108 Discharge    -   110 Input connection    -   112 Line    -   114 Output connection    -   116 Line    -   118 Electrical input    -   120 Central plug    -   122 Interface    -   124 Interface    -   126 Rotational speed sensor    -   128 Rotational speed sensor    -   130 Pressure controller    -   132 Multiple-circuit protection valve    -   134 Pressure limiter    -   136 Pressure limiter    -   138 Reservoir    -   140 Reservoir    -   142 Input    -   144 Input    -   146 Input

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A compressed air supply system for a utility vehicle, comprising: acompressor drivable by a drive via a pneumatically switchable coupling,a valve, actuatable by an electrical signal, for selective delivery ofcompressed air to a switch input of the coupling via a pressure deliveryline; and wherein the compressed air supplied to the switch input viathe valve is extracted from a compressed air preprocessing system via anonreturn valve, the nonreturn valve being adapted to prevent a pressurebreakdown in the pressure delivery line due to changes in pressure inthe regions of the compressed air preprocessing system and the consumersconnected thereto.
 2. The compressed air supply system as claimed inclaim 1, wherein the nonreturn valve is integrated into the compressedair preprocessing system.
 3. The compressed air supply system as claimedin claim 1, wherein the valve is arranged in a region of a fresh airsupply to the compressor.
 4. The compressed air supply system as claimedin claim 2, wherein the valve is arranged in a region of a fresh airsupply to the compressor.
 5. The compressed air supply system as claimedin claim 1, wherein the valve is an electrically pilot-controllablepneumatic valve.
 6. The compressed air supply system as claimed in claim2, wherein the valve is an electrically pilot-controllable pneumaticvalve.
 7. The compressed air supply system as claimed in claim 3,wherein the valve is an electrically pilot-controllable pneumatic valve.8. The compressed air supply system as claimed in claim 1, wherein theelectrical signal is made available by a pressure switch which respondsto a pressure in the compressed air preprocessing system.
 9. Thecompressed air supply system as claimed in claim 1, wherein theelectrical signal is made available by an electronic control, whichreceives pressure-dependent input signals.
 10. The compressed air supplysystem as claimed in claim 1, wherein the electrical signal is madeavailable by an electronic control, which receives temperature-dependentinput signals.
 11. The compressed air supply system as claimed in claim9, wherein the electrical signal is made available by an electroniccontrol, which receives temperature-dependent input signals.
 12. Thecompressed air supply system as claimed in claim 1, wherein theelectrical signal is made available by an electronic control, whichreceives input signals dependent on an input-side and/or an output-siderotational speed of the coupling.
 13. The compressed air supply systemas claimed in claim 9, wherein the electrical signal is made availableby an electronic control, which receives input signals dependent on aninput-side and/or an output-side rotational speed of the coupling. 14.The compressed air supply system as claimed in claim 10, wherein theelectrical signal is made available by an electronic control, whichreceives input signals dependent on an input-side and/or an output-siderotational speed of the coupling.
 15. The compressed air supply systemas claimed in claim 11, wherein the electrical signal is made availableby an electronic control, which receives input signals dependent on aninput-side and/or an output-side rotational speed of the coupling. 16.The compressed air supply system as claimed in claim 9, wherein theelectronic control is integrated into the compressed air preprocessingsystem.
 17. The compressed air supply system as claimed in claim 10,wherein the electronic control is integrated into the compressed airpreprocessing system.
 18. The compressed air supply system as claimed inclaim 12, wherein the electronic control is integrated into thecompressed air preprocessing system.
 19. The compressed air supplysystem as claimed in claim 1, wherein the electronic controlcommunicates via an interface with a control integrated into thecompressed air preprocessing system.
 20. A utility vehicle, comprising:a compressed air supply system comprising: a compressor drivable by adrive via a pneumatically switchable coupling, a valve, actuatable by anelectrical signal, for selective delivery of compressed air to a switchinput of the coupling via a pressure delivery line; and wherein thecompressed air supplied to the switch input via the valve is extractedfrom a compressed air preprocessing system via a nonreturn valve, thenonreturn valve being adapted to prevent a pressure breakdown in thepressure delivery line due to changes in pressure in the regions of thecompressed air preprocessing system and the consumers connected thereto.